The present invention relates to a known freight car truck assembly including a pair of laterally spaced side frames which are each carried by a pair of wheelsets, the side frames being spanned by a transversely extending bolster. Each side frame has an opening which receives a corresponding end of the bolster, and the ends of the bolster are supported by spring groups housed within the respective side frame openings.
In addition to the foregoing known structure, it is also known to provide a pair of friction wedges for supporting each end of the bolster, one wedge being positioned in a corresponding bolster pocket formed in longitudinally spaced sides of each bolster end. Such friction wedges are supported by wedge springs which urge each friction wedge upwardly in the bolster pocket between the bolster and a wear surface which comprises a side frame column.
As the bolster end moves vertically, each friction wedge slides against the corresponding side frame column to generate damping forces. Since the spring force loading a friction wedge is a function of the spring group travel or vertical motion of the bolster, the spring force is greater when the car is loaded than when the car is empty. Thus, the damping force varies with the car weight.
U.S. Pat. No. 4,244,298, issued Jan. 13, 1981, serves to illustrate the known prior art over which the present invention is an improvement. In the '298 patent, FIG. 1 shows a pair of laterally spaced side frames 10 together with a bolster 14 which extends between the side frames with the bolster ends received in side frame openings 16 as shown in FIG. 2.
FIG. 2 of the '298 patent shows a bolster end 14 supported on spring groups 24 contained within the side frame opening 16 and supported by the side frame. FIG. 2 further shows a friction wedge 26 contained within a bolster pocket so as to bear against a sloping wall of the bolster pocket and also against a wear surface on a side frame column 22. A wedge spring 28 urges the wedge 26 upwardly between the bolster and the side frame column. A similar wedge and related structure is provided at the longitudinally opposite side of the bolster end in an opposed bolster pocket (not shown in FIG. 2).
FIG. 3 of the '298 patent, which uses different reference numbers from FIGS. 1 and 2, affords an enlarged view of an end of a bolster 40 having opposed bolster pockets 42 at longitudinally opposite sides of the bolster end, which pockets receive corresponding wedges 52. Each wedge 52 has a friction surface 56 which frictionally engages the opposed column end surface 50 of the side frame column 44. In addition, the wedge has a surface 48 sloping at an angle of approximately 35 degrees relative to opposed column end surface 50. The sloping wedge surface 48 frictionally engages the opposed sloping surface 54 of the bolster pocket 42 formed in bolster 40. The pocket 42 accommodates the wedge 52 which is urged upwardly between the side frame column 44 and the bolster surface 54 by the wedge spring 60.
Reference is now made to FIGS. 19 and 20 of the '298 patent. FIG. 19 shows opposed pockets 42 of the bolster 40 with a wedge 52 positioned in each pocket. Each pocket 42 is shown as having a conventional, flat bolster pocket surface 54 which is engaged by a similar surface 48 on the wedge 52. The surfaces 48 and 54 are sloping surfaces, but they are flat.
A different embodiment is shown in FIG. 20 where each wedge 52 is replaced by a pair of spaced wedges 52a and 52b, the sloping back wall 48 of the bolster pocket comprises a pair of sloping surfaces, and the inner ends of the pair of wedges have similar sloping surfaces. Thus, in FIG. 20, the bottom of the bolster pocket, in addition to sloping as shown in FIG. 3, is made to slope from each sidewall 46 of the bolster pocket toward the center of the pocket and toward the opening into the pocket. The sloping sections 64 of the bolster pocket are flat across the width thereof and merge along the length thereof to form a rectilinear crown 65 disposed midway between the opposed sidewalls of the bolster pocket.
In the FIG. 20 arrangement, the wedge is formed in two separate sections 52a and 52b disposed side-by-side in the pocket 42a in slightly spaced relation to one another. The sloping surfaces of the wedge sections are beveled, and the beveled surfaces 62 are disposed in full-face engagement with the opposed sloping sections 64 of the pocket, while the remote sides of the wedge sections 58a are in full-face engagement respectively with the opposed sides 46 of the pocket. The foregoing arrangement permits the wedge spring 60 to urge both sections of the wedge against the sideframe column 44 due to the sloping surfaces as shown in FIG. 3. Simultaneously, the wedge sections are separately urged respectively against the bolster pocket sidewalls 46 due to the sloping surfaces shown at 62 and 64 in FIG. 20.
Still referring to the sloping surfaces 64 of the bolster pocket as shown in FIG. 20, such surfaces are commonly formed by casting them as part of the bolster pocket. However, another known option is to provide an insert which has the two approximately 15-degree slopes, and weld that insert into a bolster pocket of the type shown in FIG. 19 of the aforementioned '298 patent. Thus, where a bolster pocket has a flat bottom as shown in FIG. 19 of the '298 patent, one may convert the structure to the type shown in FIG. 20 of the patent by welding an insert in the pocket to create those 15-degree slopes, and then the split wedge members as shown at 52a and 52b in FIG. 20 may be used in place of the single wedges shown in FIG. 19. Such inserts are known in the art and are usually forged to create the desired sloping surfaces.
Reference is made to FIGS. 1-3 which show a known type of insert for converting a bolster pocket of the type shown in FIG. 19 of the aforementioned '298 patent to a pocket of the type shown in FIG. 20. FIG. 2 shows the insert 10 having a flat surface 12 on one side and a pair of sloping surfaces 14 and 16 on the opposite side. The sloping surfaces meet in the center to form a line 18. FIG. 3 shows how the merged surfaces at line 18 have a curved shape.
The use of split wedges as shown in FIG. 20 of the '298 patent have advantages over the single wedges shown in FIG. 19 of the patent. However, where the sloping shape has not been cast into the bolster pocket, the known forged inserts must be welded into the pocket to convert from the FIG. 19 design to the FIG. 20 design. One disadvantage of such inserts is that the welding operation involves an added expense.
The foregoing welding operation is a significant procedure because the forged insert must be welded around the sides and top. The main object of the present invention is to provide an insert which is modified in a manner which permits it to be used for the same purpose as known inserts, but without any need for welding the insert in place. Thus, the added expense of the welding operation is eliminated.
The foregoing and other objects and advantages of the invention will be apparent from the following description of a preferred embodiment thereof, taken in conjunction with the accompanying drawings.